Growth velocity and the topography of Ni-Zn binary alloy electrodeposits

We show that the electrodeposition of Ni-Zn alloys at the lowest growth velocities, $v < 0.5 \mu$m/s, exclusively proceeds from an abnormal co-deposition phenomenon. The growth process in this v region greatly depends on the initial [ Co2+] concentration of the film deposition bath. A theoretical approach of this process including the role of the saturation surface roughness of the alloy, $\sigma_{\rm sat}$, leads to an estimation of the transport properties of the ad-atoms involved during the deposit formation. Their surface diffusion coefficient varying between $1.76\times 10^{-10}$ and $2.40\times 10^{-8}$ cm-2/s exhibits a minimal value, $D_{\rm s} = 2.10\times 10^{-10}$ cm-2/s located between v = 0.17 and $0.35 \mu$m/s. The spatial scaling analysis of the local roughness, σ, examined according to the power-law $\sigma\approx L^{\alpha}$ reveals that the resulting roughness exponents concurs with the Kardar-Parisi-Zhang dynamics including the restricted surface diffusion. Two main v regions leads to different fractal textural features of the alloy film surface. Below 0.10 μm/s, the roughness exponent obtained is $\alpha\approx 0.6$, depicting a limited ad-atom mobility. Over $v = 0.30 \mu$m/s, this exponent stabilises at $\alpha\approx 0.82$, indicating an increase of the surface diffusion

Nonlinear Optical Study of Nano-Sized Effects in a-Si: H Thin Films Deposited by RF-Glow Discharge

We have evidenced the high sensitivity of infrared-induced second harmonic generation (IR-ISHG) to the structural changes occurred in amorphous hydrogenated silicon films (a-Si: H) prepared by RF-glow discharge technique at different substrate temperatures and doping types. In every case, a maximal signal of the IR-induced SHG is achieved at temperature of about 110 K and pump-probe delaying time about 22–39 ps. It indicates a marked effect of doped subsystems in the observed nonlinear optical effects. A substantial effect of doping is established from a drastic change of the IR-induced SHG behavior presenting an anomaly at about 400 MW/cm2 for a pumping power with wavelength 1.54 μm. A minimum of the SHG is observed in that case for standard nondoped films. Note here that the doping type does not affect the behavior of the second-order nonlinear optical susceptibility. The thermo annealing leads to a slight decrease of the effective second-order susceptibilities. Larger changes are observed with doped samples for the pump-probe delaying time from about 39 till 24 ps